Field of the Invention
The present invention relates to a technique capable of recognizing a multi-touch operation.
Description of the Related Art
In a user interface (UI) allowing users to input instructions via a touch panel, a multi-touch operation is generally used, which is an operation to perform input in cooperation with a plurality of touch positions with each other. In a case where a system is configured to enable a plurality of users to simultaneously perform operations, it is necessary to discriminate whether a plurality of detected touch positions has been input by a single user with intention to perform a multi-touch operation or unintentionally input by a plurality of users.
As discussed in Japanese Patent Application Laid-Open No. 2014-16795, it is feasible to discriminate an input by a single user from an input by a plurality of users based on the direction of each finger that can be estimated with reference to an area size and a shape of each finger that contacts the touch panel.
As a recently available technique, it is conventionally known to extract an area including a specific object (e.g., user's hand) from an image captured by a visible light camera, an infrared ray camera, or a range image sensor and recognize a gesture having been input as a user interface (UI) operation based on the movement and position of the specific object. Such a system is configured to acquire a distance from a finger to a touch target surface (e.g., a wall or a table) by measuring a three-dimensional position of the finger, and determine the presence of any contact based on the acquired distance value.
Even in the above-mentioned touch system, it is desired that a user can input a multi-touch operation. However, as discussed in Japanese Patent Application Laid-Open No. 2014-16795, it is unfeasible to obtain information about a finger contact surface from an arbitrary wall or table. Further, in a case where the system is sufficiently large in size and enables a plurality of users to simultaneously perform operations, each user can flexibly operate the system from various angles. Accordingly, even if the direction of a finger is detectable at a portion other than the touch panel, it is difficult to obtain an accurate identification result because there is not so large difference in direction angle between fingers of a plurality of users if the users are positioned adjacently.